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EP1641608A2 - Method for preparing beads based on expanded polymer - Google Patents

Method for preparing beads based on expanded polymer

Info

Publication number
EP1641608A2
EP1641608A2 EP04767525A EP04767525A EP1641608A2 EP 1641608 A2 EP1641608 A2 EP 1641608A2 EP 04767525 A EP04767525 A EP 04767525A EP 04767525 A EP04767525 A EP 04767525A EP 1641608 A2 EP1641608 A2 EP 1641608A2
Authority
EP
European Patent Office
Prior art keywords
equal
polymer
pearl
blowing agent
preferably less
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP04767525A
Other languages
German (de)
French (fr)
Other versions
EP1641608B1 (en
Inventor
Jean-François ESTUR
Eric Roche
Jean-François BRIOIS
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Rhodia Operations SAS
Original Assignee
Rhodia Polyamide Intermediates SAS
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Rhodia Polyamide Intermediates SAS filed Critical Rhodia Polyamide Intermediates SAS
Publication of EP1641608A2 publication Critical patent/EP1641608A2/en
Application granted granted Critical
Publication of EP1641608B1 publication Critical patent/EP1641608B1/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C44/00—Shaping by internal pressure generated in the material, e.g. swelling or foaming ; Producing porous or cellular expanded plastics articles
    • B29C44/34—Auxiliary operations
    • B29C44/3461—Making or treating expandable particles
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T428/00—Stock material or miscellaneous articles
    • Y10T428/249921—Web or sheet containing structurally defined element or component
    • Y10T428/249953—Composite having voids in a component [e.g., porous, cellular, etc.]
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T428/00—Stock material or miscellaneous articles
    • Y10T428/249921—Web or sheet containing structurally defined element or component
    • Y10T428/249953—Composite having voids in a component [e.g., porous, cellular, etc.]
    • Y10T428/249987—With nonvoid component of specified composition

Definitions

  • the present invention relates to a process for preparing an article based on expanded polymer.
  • the invention relates more particularly to a process for preparing a pearl based on expanded polymer.
  • Expanded synthetic materials are used in many fields, such as thermal or sound insulation, upholstery etc.
  • foams also called foams: structural foams and non-structural foams.
  • Structural foams are rigid foams composed of a low density core and a skin whose density is close to that of the polymer making up the matrix. These foams can be used as lightweight structures in the aeronautics or automotive fields for example.
  • Non-structural foams can be flexible or rigid. Rigid foams are used in the field of thermal insulation (the gas present in the cells acts as an insulator).
  • thermoplastic polymer foams such as polystyrene, PVC, polyethylene, polypropylene foams, etc., and in particular polyamide foams. It is known to inject gases under pressure into the polymer in the molten state. It is also known to incorporate porophores - thermally unstable charges - into the polymer in the molten state, which release a gas during their decomposition.
  • thermoplastic polymer foams and in particular polyamide foams, are generally shaped by molding, for example by injection-molding. The articles thus obtained are generally used as such for various applications.
  • the expanded polymer material is introduced into other materials. This is the case in particular in the field of light materials, of light concrete type.
  • an expanded material is sought in an easily handled form, dispersible in the matrix, etc.
  • Acicular fillers are known for this type of application.
  • their shape is penalizing in particular in terms of viscosity when they are introduced into the matrix, which limits for example the quantity of fillers which it is possible to incorporate into the matrix.
  • the spherical shape of the charges incorporated for example in concrete therefore has an advantage; they also allow optimization of the stack in the material.
  • an article is made of expanded material having closed porosity.
  • the present invention provides, in a first object, a process for preparing a pearl based on expanded polymer and with continuous skin, comprising the following successive steps: a) extruding through a die a foamable composition comprising a thermoplastic polymer and an agent for expansion, in the molten state, to carry out the expansion b) cooling and cutting the expanded material directly at the outlet of the die using a knife
  • the invention also relates to a pearl based on expanded polyamide and with skin keep on going.
  • pearl is meant a small article whose largest dimension is less than or equal to 15 mm.
  • pearl means a spherical or essentially spherical article.
  • continuous skin pearl is meant a pearl having no surface porosity.
  • a pearl having no porosity by observation with a scanning electron microscope up to a magnification of at least 5000.
  • Any thermoplastic polymer can be used in the context of the invention.
  • a thermoplastic polymer mention may be made of polyamides, polyesters, polyurethanes, polyolefins such as polyethylene or polypropylene, polystyrene, etc.
  • the thermoplastic polymer is a polyamide. Any polyamide known to a person skilled in the art can be used in the context of the invention.
  • the polyamide is generally a polyamide of the type of those obtained by polycondensation from dicarboxylic acids and diamines, or of the type of those obtained by polycondensation of lactams and / or amino acids.
  • the polyamide of the invention may be a mixture of polyamides of different types and / or of the same type, and / or copolymers obtained from different monomers corresponding to the same type and / or to different types of polyamide.
  • polyamide 6 As an example of a polyamide which may be suitable for the invention, mention may be made of polyamide 6, polyamide 6.6, polyamide 11, polyamide 12, polyamides 4.6; 6.10; 6.12; 12.12, 6.36; semi-aromatic polyamides, for example polyphthalamides obtained from terephthalic and / or isophthalic acid such as the polyamide sold under the trade name AMODEL, their copolymers and alloys.
  • the polyamide is chosen from polyamide 6, polyamide 6.6, their mixtures and copolymers. Any expandable composition comprising a thermoplastic polymer and a blowing agent can be used in the context of the invention, as well as any method for preparing it.
  • the blowing agent is a gas which can disperse or dissolve in the polymer in the molten state.
  • the composition according to this embodiment is generally prepared by introducing the gas into the molten polymer, according to a method known to those skilled in the art. Any gas known to a person skilled in the art which can disperse or dissolve in the polymer of the invention can be used.
  • the gas is preferably inert.
  • a suitable gas in the context of the invention there may be mentioned nitrogen, carbon dioxide, butane, etc.
  • the blowing agent is a pore-forming agent. Any blowing agent known to those skilled in the art can be used.
  • the temperature during step a) is preferably greater than or equal to the decomposition temperature of the blowing agent.
  • the blowing agent is a volatile compound which can dissolve in the polymer in the molten state.
  • the composition according to this embodiment is generally prepared by introduction of the volatile compound into the molten polymer, according to a method known to those skilled in the art. Any volatile compound known to a person skilled in the art which can dissolve in the polymer of the invention can be used.
  • the blowing agent is a chemical compound which can react chemically with the polymer by heating.
  • a gas is generally generated during this reaction, gas which is at the origin of the expansion of the mixture.
  • These chemical compounds are known to those skilled in the art.
  • polycarbonate which reacts with polyamide and decomposes to generate carbon dioxide.
  • the chemical reaction takes place during step a). Any method known to a person skilled in the art for preparing the composition can then be used.
  • step a) it is possible, for example, to produce an intimate mixture of the powders of the polymer and of the chemical compound, or a mixture of the polymer granules and of the granules of the chemical compound.
  • the polymer can also be in the form of granules, which are coated with the chemical compound.
  • Another mode of preparation of the composition is the pasting of the various compounds. It is also possible to introduce the chemical compound into the polymer in the molten state.
  • the temperature during step a) must be sufficient for there to be a reaction between the polymer and the chemical compound, and generation of gas.
  • a combination of the various embodiments described above can be used to prepare the foamable composition of the process of the invention.
  • the expandable composition may include additives such as surfactants, nucleators such as talc, plasticizers, etc. These additives are known to those skilled in the art.
  • the expandable composition may also include other compounds, such as reinforcing fillers such as glass fibers, matifiers such as titanium dioxide or zinc sulfide, pigments, dyes, heat or light stabilizers, agents bioactive, antifouling agents, antistatic agents, flame retardants etc. This list is not exhaustive.
  • step a) is advantageously carried out in a kneading device capable of generating a pressure greater than atmospheric pressure. Step a) is preferably carried out in an extruder, even more preferably in a twin-screw extruder.
  • the expandable composition can be prepared according to a method described above, then introduced into the extrusion device used during step a).
  • the composition can be introduced in solid or liquid form, for example in the molten state.
  • the expandable composition can also be prepared in situ in the same extrusion device as that used in step a), before extruding the composition according to step a).
  • the gas or respectively the volatile compound can be introduced into the sleeve or the piston of the extrusion device of step a), comprising the polymer of the expandable composition in the molten state.
  • Step a) which consists in extruding the composition through a die to carry out the expansion is carried out in a conventional manner and known to those skilled in the art.
  • Step b) consisting in cooling and cutting the expanded material, is advantageously carried out using a cutting granulation device disposed at the outlet of the die.
  • a granulation device is known to those skilled in the art. It comprises at least one cutting device which faces the die plate through which the polymer is extruded, and a cooling device.
  • the cutting device generally comprises knives, a knife holder, and a motor for driving the knife holder.
  • the knife holder is usually rotatable.
  • the cooling device may consist of a device for spraying cold water located near the cutting device and the die plate.
  • the cutting device and the die plate can also be placed in a chamber filled with water. This is the case of “overhead” cut granulators known to those skilled in the art.
  • the water In this chamber filled with water, the water is generally in circulation and it ensures the cooling and the transport of the polymer beads formed at the level of the cutting device towards a dryer.
  • the drying can be carried out using a centrifuge which separates the water and the pearls, or using a cycloning device.
  • Such granulator devices with a “submerged head cut” are for example described in American patent US Pat. No. 5,059,103.
  • the cooling of the expanded material makes it possible in particular to freeze the latter.
  • the water in the cooling device can be replaced by another liquid, generally used as a solvent.
  • the cooling of step b) is therefore carried out using a liquid, preferably using water.
  • the use of such “head cut” granulators in the context of the invention makes it possible to obtain beads based on expanded polymer and with continuous skin. It also allows the production of pearls with good productivity.
  • the pearl obtained according to the method of the invention advantageously has a diameter less than or equal to 10 mm, preferably less than or equal to 5 mm.
  • the size of the pearl depends on several parameters; it depends in particular on the diameter of the die holes, the extrusion rate and the cutting frequency.
  • the pearl obtained according to the process of the invention advantageously has a density less than or equal to 0.8 g / cm 3 , preferably less than or equal to 0.5 g / cm 3 , even more preferably less than or equal to 0, 3 g / cm 3 .
  • the density of the pearl of the invention is measured according to the protocol described in the experimental part.
  • the invention also relates to beads based on expanded polyamide or polyester and with continuous skin. This pearl based on polyamide or polyester advantageously has a diameter less than or equal to 10 mm, preferably less than or equal to 5 mm.
  • the pearl based on polyamide or polyester of the invention advantageously has a density less than or equal to 0.8 g / cm 3 , preferably less than or equal to 0.5 g / cm 3 , even more preferably less than or equal at 0.3 g / cm 3 .
  • the density of the pearl based on polyamide or polyester of the invention is measured according to the protocol described in the experimental part.
  • the pearls based on expanded polymer of the invention can be used as such in many fields, such as building or aeronautics, as a lightening structure for example. They can also be introduced into a molding device, for example for thermocompression molding. Other details or advantages of the invention will appear more clearly on seeing the examples given below and with reference to the appended figures, which do not constitute a limitation to the invention.
  • FIG. 1 represents a top view of the pearl of the invention, observed with a scanning microscope.
  • FIG. 2 represents a sectional view of the pearl of the invention, observed with a scanning microscope.
  • the temperature profile on the heating elements of the twin-screw are (in ° C) 270-280-280-280-280-280, the adapter is maintained at 272 ° C and the die heated to 330 ° C.
  • the screw rotation speed is fixed at 201 turns.
  • FIG. 1 represents a top view of the pearl of the invention, observed under a scanning microscope.
  • the continuous skin of the pearl can be seen in this figure
  • Figure 2 shows a sectional view of the pearl of the invention, observed with a scanning microscope, The continuous skin of the pearl and its internal porosity can be observed in this figure.
  • Example 2 A mixture of PET granules sold by the company Wellman under the reference Permaclear VI 84® (85% w / w) and polycarbonate granules sold by the company GE Plastics under the reference Lexan 121-111® (15% w / p) is introduced into a twin-screw extruder sold by the company Leistriz under the reference TSA-EMP 26-35®, equipped with a submerged head cutting system sold by the company Gala under the reference LPU Mod 5.
  • the profile of temperature on the heating elements of the twin screw are (in ° C) 280-300-315-335-275, the adapter is maintained at 272 ° C and the die heated to 330 ° C.
  • the screw rotation speed is fixed at 200 turns. min "1.
  • the extrusion rate is 15 kg / h.
  • the die consists of a single orifice with a diameter of 2.4 mm.
  • the cutting water is maintained at 85 ° C.
  • the knife holder has two knives and the cutting frequency is 2800 rpm. This method produces rigid expanded PET granules with a density of 0.7 g / cm 3 .

Landscapes

  • Manufacture Of Porous Articles, And Recovery And Treatment Of Waste Products (AREA)
  • Molding Of Porous Articles (AREA)
  • Processing And Handling Of Plastics And Other Materials For Molding In General (AREA)
  • Compositions Of Macromolecular Compounds (AREA)

Abstract

The invention concerns a method for preparing an article based on expanded polymer. More particularly, the invention concerns a method for making beads based on expanded polymer.

Description

PROCEDE DE PREPARATION DE PERLE A BASE DE POLYMERE EXPANSE PROCESS FOR THE PREPARATION OF PEARLS BASED ON EXPANDED POLYMER
La présente invention concerne un procédé de préparation d'un article à base de polymère expansé. L'invention concerne plus particulièrement un procédé de préparation d'une perle à base de polymère expansé. Les matériaux synthétiques expansés sont utilisés dans de nombreux domaines, tels que l'isolation thermique ou phonique, la sellerie etc. On distingue essentiellement deux types de matériaux expansés, également appelés mousses : les mousses structurelles et les mousses non structurelles. Les mousses structurelles sont des mousses rigides composées d'un cœur de faible densité et d'une peau dont la densité est proche de celle du polymère composant la matrice. Ces mousses peuvent être utilisées comme structures allégées dans le domaine de l'aéronautique ou de l'automobile par exemple. Les mousses non structurelles peuvent être flexibles ou rigides. Les mousses rigides sont utilisées dans le domaine de l'isolation thermique (le gaz présent dans les cellules joue le rôle d'isolant). Les mousses flexibles sont utilisées dans le domaine de l'ameublement et de la sellerie, pour leurs propriétés de compressibilité et d'amortissement, dans le domaine de l'emballage en raison de leur faible poids, ainsi que dans le domaine de l'isolation phonique (les mousses présentant une porosité ouverte ont la particularité d'absorber certaines fréquences). On connaît différentes méthodes pour obtenir des mousses de polymère thermoplastique, telles que des mousses de polystyrène, de PVC, de polyéthylène, de polypropylène, etc, et notamment des mousses de polyamide. Il est connu d'injecter des gaz sous pression dans le polymère à l'état fondu. II est également connu d'incorporer des porophores -charges instables thermiquement- dans le polymère à l'état fondu, qui libèrent un gaz lors de leur décomposition. Il est également possible de dissoudre ou de disperser des composés dans le polymère à l'état fondu, la mousse étant obtenue par volatilisation de ces composés. Enfin, il est connu d'obtenir des mousses à l'aide d'une réaction chimique dégageant du gaz, comme du dioxyde de carbone. C'est le cas par exemple des mousses polyuréthane obtenues par réaction entre des isocyanates, des polyols et de l'eau conduisant à la formation de polyuréthane avec libération de dioxyde de carbone. Des mousses de polyamide peuvent également être obtenues par voie chimique, en mettant en présence des isocyanates et des lactames ainsi que des bases pour activer la polymérisation anionique. Ces mousses de polymère thermoplastique, et notamment les mousses de polyamide, sont généralement mises en forme par moulage, par exemple par injection- moulage. Les articles ainsi obtenus sont généralement utilisés tels quels pour diverses applications. Or pour certaines applications, le matériau en polymère expansé est introduit au sein d'autres matériaux. C'est le cas notamment dans le domaine des matériaux allégés, de type béton allégé. On recherche dans ce type d'applications un matériau expansé sous une forme aisément manipulable, dispersible dans la matrice etc. Des charges aciculaires sont connues pour ce type d'application. Mais leur forme est pénalisante notamment en terme de viscosité lors de leur introduction dans la matrice, ce qui limite par exemple la quantité de charges qu'il est possible d'incorporer dans la matrice. La forme sphérique des charges incorporées par exemple dans le béton, présente donc un avantage ; elles permettent en outre une optimisation de l'empilement dans le matériau. De plus, pour certaines applications spécifiques telles que les bétons allégés, on recherche un article en matériau expansé présentant une porosité fermée. Ceci afin d'éviter notamment une absorption d'eau par l'article en matériau expansé, lors de la préparation du béton. La présente invention propose dans un premier objet un procédé de préparation d'une perle à base de polymère expansé et à peau continue, comprenant les étapes successives suivantes : a) extruder à travers une filière une composition expansible comprenant un polymère thermoplastique et un agent d'expansion, à l'état fondu, pour réaliser l'expansion b) refroidir et couper le matériau expansé directement en sortie de filière à l'aide d'un couteau L'invention concerne également une perle à base de polyamide expansé et à peau continue. Par perle on entend un article de petite taille dont la plus grande dimension est inférieure ou égale à 15 mm. De préférence on entend par perle un article sphérique ou essentiellement sphérique. Par perle à peau continue, on entend une perle ne présentant pas de porosité de surface. De préférence on entend par perle à peau continue une perle ne présentant pas de porosité par observation au microscope électronique à balayage jusqu'à un grossissement d'au moins 5000. Tout polymère thermoplastique peut être mis en œuvre dans le cadre de l'invention. A titre d'exemple de polymère thermoplastique, on peut citer les polyamides, les polyesters, les polyuréthanes, les polyoléfines telles que le polyéthylène ou le polypropylène, le polystyrène etc. Selon un mode de réalisation particulier du procédé de l'invention, le polymère thermoplastique est un polyamide. Tout polyamide connu de l'homme du métier peut être utilisé dans le cadre de l'invention. Le polyamide est généralement un polyamide du type de ceux obtenus par polycondensation à partir de diacides carboxyliques et de diamines, ou du type de ceux obtenus par polycondensation de lactames et/ou aminoacides. Le polyamide de l'invention peut être un mélange de polyamides de différents types et/ou du même type, et/ou des copolymères obtenus à partir de différents monomères correspondant au même type et/ou à des types différents de polyamide. A titre d'exemple de polyamide pouvant convenir pour l'invention, on peut citer le polyamide 6, le polyamide 6,6, le polyamide 11 , le polyamide 12, les polyamides 4,6 ; 6,10 ; 6,12 ; 12,12, 6,36 ; les polyamides semi-aromatiques, par exemple les polyphtalamides obtenus à partir d'acide téréphtalique et/ou isophtalique tels que le polyamide commercialisé sous le nom commercial AMODEL, leurs copolymères et alliages. Selon un mode de réalisation préférentiel de l'invention, le polyamide est choisi parmi le polyamide 6, le polyamide 6,6, leurs mélanges et copolymères. Tout composition expansible comprenant un polymère thermoplastique et un agent d'expansion peut être utilisée dans le cadre de l'invention, ainsi que toute méthode pour la préparer. Selon un premier mode de réalisation particulier du procédé de l'invention, l'agent d'expansion est un gaz pouvant se disperser ou se dissoudre dans le polymère à l'état fondu. La composition selon ce mode de réalisation est généralement préparée par introduction du gaz dans le polymère fondu, selon une méthode connue de l'homme du métier. Tout gaz connu de l'homme du métier pouvant se disperser ou se dissoudre dans le polymère de l'invention peut être utilisé. Le gaz est de préférence inerte. On peut citer comme exemple de gaz convenable dans le cadre de l'invention l'azote, le dioxyde de carbone, le butane etc. Selon un deuxième mode de réalisation particulier du procédé de l'invention, l'agent d'expansion est un agent porogène. Tout agent porogène connu de l'homme du métier peut être utilisé. Il est introduit dans le polymère selon une méthode connue de l'homme du métier. On peut citer comme exemple d'agent porogène le diazocarbonamide. Selon ce mode particulier, la température lors de l'étape a) est de préférence supérieure ou égale à la température de décomposition de l'agent porogène. Selon un troisième mode de réalisation particulier du procédé de l'invention, l'agent d'expansion est un composé volatile pouvant se dissoudre dans le polymère à l'état fondu. La composition selon ce mode de réalisation est généralement préparée par introduction du composé volatile dans le polymère fondu, selon une méthode connue de l'homme du métier. Tout composé volatile connu de l'homme du métier pouvant se dissoudre dans le polymère de l'invention peut être utilisé. On peut citer comme exemple de composé volatile convenable dans le cadre de l'invention le butanol. Selon un quatrième mode de réalisation particulier du procédé de l'invention, l'agent d'expansion est un composé chimique pouvant réagir chimiquement avec le polymère par chauffage. Un gaz est généralement généré lors de cette réaction, gaz qui est à l'origine de l'expansion du mélange. Ces composés chimiques sont connus de l'homme du métier. On peut par exemple citer le polycarbonate, qui réagit avec le polyamide et se décompose pour générer du dioxyde de carbone. La réaction chimique intervient lors de l'étape a). Toute méthode connue de l'homme du métier pour préparer la composition peut alors être utilisée. On peut par exemple réaliser un mélange intime des poudres du polymère et du composé chimique, ou un mélange des granulés de polymère et des granulés du composé chimique. Le polymère peut également se présenter sous la forme de granulés, que l'on enrobe par le composé chimique. Un autre mode de préparation de la composition est l'empâtage des différents composés. Il est également possible d'introduire le composé chimique dans le polymère à l'état fondu. Selon ce quatrième mode de réalisation, la température lors de l'étape a) doit être suffisante pour qu'il y ait réaction entre le polymère et le composé chimique, et génération de gaz. Une combinaison des différents modes de réalisation décrits ci-dessus peuvent être mis en œuvre pour préparer la composition expansible du procédé de l'invention. La composition expansible peut comprendre des additifs tels que des surfactants, des nucleants comme le talc, des plastifiants etc. Ces additifs sont connus de l'homme du métier. La composition expansible peut également comprendre d'autres composés, tels que des charges de renfort comme les fibres de verre, des matifiants comme le dioxyde de titane ou le sulfure de zinc, des pigments, des colorants, des stabilisants chaleur ou lumière, des agents bioactifs, des agents antisalissure, des agents antistatiques, des ignifugeants etc. Cette liste n'a aucun caractère exhaustif. Dans le cadre de l'invention, l'étape a) est avantageusement réalisée dans un dispositif de malaxage pouvant générer une pression supérieure à la pression atmosphérique. L'étape a) est de préférence réalisée dans une extrudeuse, encore plus préférentiellement dans une extrudeuse bi-vis. La composition expansible peut être préparée selon un mode décrit ci-dessus, puis introduite dans le dispositif d'extrusion mis en œuvre lors de l'étape a). La composition peut être introduite sous forme solide ou liquide, par exemple à l'état fondu. La composition expansible peut également être préparée in situ dans le même dispositif d'extrusion que celui mis en œuvre lors de l'étape a), avant l'extrusion de la composition selon l'étape a). Par exemple lorsque la composition expansible est conforme au premier ou au troisième mode de réalisation particulier décrits ci-dessus, le gaz ou respectivement le composé volatile peuvent être introduits dans le fourreau ou le piston du dispositif d'extrusion de l'étape a), comprenant le polymère de la composition expansible à l'état fondu. L'étape a) qui consiste à extruder la composition à travers une filière pour réaliser l'expansion est mise en œuvre d'une manière classique et connue de l'homme du métier. L'étape b) consistant à refroidir et couper la matériau expansé, est avantageusement réalisée à l'aide d'un dispositif de granulation à coupe disposé à la sortie de la filière. Un tel dispositif de granulation est connu de l'homme du métier. Il comprend au moins un dispositif de coupe qui fait face à la plaque de filière à travers laquelle le polymère est extrudé, et un dispositif de refroidissement. Le dispositif de coupe comprend généralement des couteaux, un porte-couteaux, et un moteur pour entraîner le porte-couteaux. Le porte-couteaux est habituellement rotatif. Le dispositif de refroidissement peut consister en un dispositif de pulvérisation d'eau froide situé à proximité du dispositif de coupe et de la plaque de filière. C'est le cas des granulateurs à « coupe à chaud» connus de l'homme du métier. Le dispositif de coupe et la plaque filière peuvent également être disposés dans une chambre remplie d'eau. C'est le cas des granulateurs à « coupe en tête noyée » connus de l'homme du métier. Dans cette chambre remplie d'eau, l'eau est généralement en circulation et elle assure le refroidissement et le transport des perles de polymère formées au niveau du dispositif de coupe vers un sécheur. Le séchage peut être réalisé à l'aide d'une centrifugeuse qui sépare l'eau et les perles, ou à l'aide d'un dispositif de cyclonage. De tels dispositifs de granulateurs à « coupe en tête noyée » sont par exemple décrits dans le brevet américain US 5 059103. Le refroidissement du matériau expansé permet notamment de figer ce dernier. L'eau du dispositif de refroidissement peut être remplacée par un autre liquide, généralement utilisé comme solvant. Avantageusement, le refroidissement de l'étape b) est donc réalisé à l'aide d'un liquide, de préférence à l'aide d'eau. La mise en œuvre de tels granulateurs à « coupe en tête » dans le cadre de l'invention permet l'obtention de perles à base de polymère expansé et à peau continue . Elle permet également la fabrication de perles avec une bonne productivité. La perle obtenue selon le procédé de l'invention présente avantageusement un diamètre inférieur ou égal à 10 mm, de préférence inférieur ou égal à 5 mm. La taille de la perle dépend de plusieurs paramètres ; elle dépend notamment du diamètre des trous de filière, du débit d'extrusion et de la fréquence de coupe. La perle obtenue selon le procédé de l'invention présente avantageusement une masse volumique inférieure ou égale à 0,8 g/cm3, de préférence inférieure ou égale à 0,5 g/cm3, encore plus preferentiellement inférieure ou égale à 0,3 g/cm3. La masse volumique de la perle de l'invention est mesurée selon le protocole décrit dans la partie expérimentale. L'invention concerne également des perles à base de polyamide ou de polyester expansé et à peau continue. Cette perle à base de polyamide ou de polyester présente avantageusement un diamètre inférieur ou égal à 10 mm, de préférence inférieur ou égal à 5 mm. La perle à base de polyamide ou de polyester de l'invention présente avantageusement une masse volumique inférieure ou égale à 0,8 g/cm3, de préférence inférieure ou égale à 0,5 g/cm3, encore plus preferentiellement inférieure ou égale à 0,3 g/cm3. La masse volumique de la perle à base de polyamide ou de polyester de l'invention est mesurée selon le protocole décrit dans la partie expérimentale Les perles à base de polymère expansé de l'invention peuvent être utilisées telles quelles dans de nombreux domaines, tels que le bâtiment ou l'aéronautique, comme structure d'allégement par exemple. Elles peuvent également être introduites dans un dispositif de moulage, par exemple en vue d'un moulage par thermocompression. D'autres détails ou avantages de l'invention apparaîtront plus clairement à la vue des exemples donnés ci-dessous et en référence aux figures annexées, qui ne constituent pas une limitation à l'invention. La figure 1 représente une vue de dessus de la perle de l'invention, observée au microscope à balayage. La figure 2 représente une vue en coupe de la perle de l'invention, observée au microscope à balayage.The present invention relates to a process for preparing an article based on expanded polymer. The invention relates more particularly to a process for preparing a pearl based on expanded polymer. Expanded synthetic materials are used in many fields, such as thermal or sound insulation, upholstery etc. There are essentially two types of expanded materials, also called foams: structural foams and non-structural foams. Structural foams are rigid foams composed of a low density core and a skin whose density is close to that of the polymer making up the matrix. These foams can be used as lightweight structures in the aeronautics or automotive fields for example. Non-structural foams can be flexible or rigid. Rigid foams are used in the field of thermal insulation (the gas present in the cells acts as an insulator). Flexible foams are used in the field of furniture and upholstery, for their compressibility and cushioning properties, in the field of packaging due to their low weight, as well as in the field of insulation. phonic (foams with open porosity have the particularity of absorbing certain frequencies). Various methods are known for obtaining thermoplastic polymer foams, such as polystyrene, PVC, polyethylene, polypropylene foams, etc., and in particular polyamide foams. It is known to inject gases under pressure into the polymer in the molten state. It is also known to incorporate porophores - thermally unstable charges - into the polymer in the molten state, which release a gas during their decomposition. It is also possible to dissolve or disperse compounds in the polymer in the molten state, the foam being obtained by volatilization of these compounds. Finally, it is known to obtain foams using a chemical reaction releasing gas, such as carbon dioxide. This is the case for example of polyurethane foams obtained by reaction between isocyanates, polyols and water leading to the formation of polyurethane with release of carbon dioxide. Polyamide foams can also be obtained chemically, by bringing together isocyanates and lactams as well as bases to activate the anionic polymerization. These thermoplastic polymer foams, and in particular polyamide foams, are generally shaped by molding, for example by injection-molding. The articles thus obtained are generally used as such for various applications. However, for certain applications, the expanded polymer material is introduced into other materials. This is the case in particular in the field of light materials, of light concrete type. In this type of application, an expanded material is sought in an easily handled form, dispersible in the matrix, etc. Acicular fillers are known for this type of application. However, their shape is penalizing in particular in terms of viscosity when they are introduced into the matrix, which limits for example the quantity of fillers which it is possible to incorporate into the matrix. The spherical shape of the charges incorporated for example in concrete, therefore has an advantage; they also allow optimization of the stack in the material. In addition, for certain specific applications such as lightened concretes, an article is made of expanded material having closed porosity. This in particular to avoid absorption of water by the expanded material article, during the preparation of the concrete. The present invention provides, in a first object, a process for preparing a pearl based on expanded polymer and with continuous skin, comprising the following successive steps: a) extruding through a die a foamable composition comprising a thermoplastic polymer and an agent for expansion, in the molten state, to carry out the expansion b) cooling and cutting the expanded material directly at the outlet of the die using a knife The invention also relates to a pearl based on expanded polyamide and with skin keep on going. By pearl is meant a small article whose largest dimension is less than or equal to 15 mm. Preferably pearl means a spherical or essentially spherical article. By continuous skin pearl is meant a pearl having no surface porosity. Preferably by continuous skin pearl is understood a pearl having no porosity by observation with a scanning electron microscope up to a magnification of at least 5000. Any thermoplastic polymer can be used in the context of the invention. By way of example of a thermoplastic polymer, mention may be made of polyamides, polyesters, polyurethanes, polyolefins such as polyethylene or polypropylene, polystyrene, etc. According to a particular embodiment of the process of the invention, the thermoplastic polymer is a polyamide. Any polyamide known to a person skilled in the art can be used in the context of the invention. The polyamide is generally a polyamide of the type of those obtained by polycondensation from dicarboxylic acids and diamines, or of the type of those obtained by polycondensation of lactams and / or amino acids. The polyamide of the invention may be a mixture of polyamides of different types and / or of the same type, and / or copolymers obtained from different monomers corresponding to the same type and / or to different types of polyamide. As an example of a polyamide which may be suitable for the invention, mention may be made of polyamide 6, polyamide 6.6, polyamide 11, polyamide 12, polyamides 4.6; 6.10; 6.12; 12.12, 6.36; semi-aromatic polyamides, for example polyphthalamides obtained from terephthalic and / or isophthalic acid such as the polyamide sold under the trade name AMODEL, their copolymers and alloys. According to a preferred embodiment of the invention, the polyamide is chosen from polyamide 6, polyamide 6.6, their mixtures and copolymers. Any expandable composition comprising a thermoplastic polymer and a blowing agent can be used in the context of the invention, as well as any method for preparing it. According to a first particular embodiment of the process of the invention, the blowing agent is a gas which can disperse or dissolve in the polymer in the molten state. The composition according to this embodiment is generally prepared by introducing the gas into the molten polymer, according to a method known to those skilled in the art. Any gas known to a person skilled in the art which can disperse or dissolve in the polymer of the invention can be used. The gas is preferably inert. As an example of a suitable gas in the context of the invention, there may be mentioned nitrogen, carbon dioxide, butane, etc. According to a second particular embodiment of the method of the invention, the blowing agent is a pore-forming agent. Any blowing agent known to those skilled in the art can be used. It is introduced into the polymer according to a method known to those skilled in the art. As an example of a blowing agent, diazocarbonamide may be mentioned. According to this particular mode, the temperature during step a) is preferably greater than or equal to the decomposition temperature of the blowing agent. According to a third particular embodiment of the process of the invention, the blowing agent is a volatile compound which can dissolve in the polymer in the molten state. The composition according to this embodiment is generally prepared by introduction of the volatile compound into the molten polymer, according to a method known to those skilled in the art. Any volatile compound known to a person skilled in the art which can dissolve in the polymer of the invention can be used. As an example of a volatile compound which may be used in the context of the invention, mention may be made of butanol. According to a fourth particular embodiment of the process of the invention, the blowing agent is a chemical compound which can react chemically with the polymer by heating. A gas is generally generated during this reaction, gas which is at the origin of the expansion of the mixture. These chemical compounds are known to those skilled in the art. We can for example mention polycarbonate, which reacts with polyamide and decomposes to generate carbon dioxide. The chemical reaction takes place during step a). Any method known to a person skilled in the art for preparing the composition can then be used. It is possible, for example, to produce an intimate mixture of the powders of the polymer and of the chemical compound, or a mixture of the polymer granules and of the granules of the chemical compound. The polymer can also be in the form of granules, which are coated with the chemical compound. Another mode of preparation of the composition is the pasting of the various compounds. It is also possible to introduce the chemical compound into the polymer in the molten state. According to this fourth embodiment, the temperature during step a) must be sufficient for there to be a reaction between the polymer and the chemical compound, and generation of gas. A combination of the various embodiments described above can be used to prepare the foamable composition of the process of the invention. The expandable composition may include additives such as surfactants, nucleators such as talc, plasticizers, etc. These additives are known to those skilled in the art. The expandable composition may also include other compounds, such as reinforcing fillers such as glass fibers, matifiers such as titanium dioxide or zinc sulfide, pigments, dyes, heat or light stabilizers, agents bioactive, antifouling agents, antistatic agents, flame retardants etc. This list is not exhaustive. In the context of the invention, step a) is advantageously carried out in a kneading device capable of generating a pressure greater than atmospheric pressure. Step a) is preferably carried out in an extruder, even more preferably in a twin-screw extruder. The expandable composition can be prepared according to a method described above, then introduced into the extrusion device used during step a). The composition can be introduced in solid or liquid form, for example in the molten state. The expandable composition can also be prepared in situ in the same extrusion device as that used in step a), before extruding the composition according to step a). For example, when the expandable composition is in accordance with the first or third particular embodiment described above, the gas or respectively the volatile compound can be introduced into the sleeve or the piston of the extrusion device of step a), comprising the polymer of the expandable composition in the molten state. Step a) which consists in extruding the composition through a die to carry out the expansion is carried out in a conventional manner and known to those skilled in the art. Step b) consisting in cooling and cutting the expanded material, is advantageously carried out using a cutting granulation device disposed at the outlet of the die. Such a granulation device is known to those skilled in the art. It comprises at least one cutting device which faces the die plate through which the polymer is extruded, and a cooling device. The cutting device generally comprises knives, a knife holder, and a motor for driving the knife holder. The knife holder is usually rotatable. The cooling device may consist of a device for spraying cold water located near the cutting device and the die plate. This is the case with “hot cut” granulators known to those skilled in the art. The cutting device and the die plate can also be placed in a chamber filled with water. This is the case of “overhead” cut granulators known to those skilled in the art. In this chamber filled with water, the water is generally in circulation and it ensures the cooling and the transport of the polymer beads formed at the level of the cutting device towards a dryer. The drying can be carried out using a centrifuge which separates the water and the pearls, or using a cycloning device. Such granulator devices with a “submerged head cut” are for example described in American patent US Pat. No. 5,059,103. The cooling of the expanded material makes it possible in particular to freeze the latter. The water in the cooling device can be replaced by another liquid, generally used as a solvent. Advantageously, the cooling of step b) is therefore carried out using a liquid, preferably using water. The use of such “head cut” granulators in the context of the invention makes it possible to obtain beads based on expanded polymer and with continuous skin. It also allows the production of pearls with good productivity. The pearl obtained according to the method of the invention advantageously has a diameter less than or equal to 10 mm, preferably less than or equal to 5 mm. The size of the pearl depends on several parameters; it depends in particular on the diameter of the die holes, the extrusion rate and the cutting frequency. The pearl obtained according to the process of the invention advantageously has a density less than or equal to 0.8 g / cm 3 , preferably less than or equal to 0.5 g / cm 3 , even more preferably less than or equal to 0, 3 g / cm 3 . The density of the pearl of the invention is measured according to the protocol described in the experimental part. The invention also relates to beads based on expanded polyamide or polyester and with continuous skin. This pearl based on polyamide or polyester advantageously has a diameter less than or equal to 10 mm, preferably less than or equal to 5 mm. The pearl based on polyamide or polyester of the invention advantageously has a density less than or equal to 0.8 g / cm 3 , preferably less than or equal to 0.5 g / cm 3 , even more preferably less than or equal at 0.3 g / cm 3 . The density of the pearl based on polyamide or polyester of the invention is measured according to the protocol described in the experimental part. The pearls based on expanded polymer of the invention can be used as such in many fields, such as building or aeronautics, as a lightening structure for example. They can also be introduced into a molding device, for example for thermocompression molding. Other details or advantages of the invention will appear more clearly on seeing the examples given below and with reference to the appended figures, which do not constitute a limitation to the invention. FIG. 1 represents a top view of the pearl of the invention, observed with a scanning microscope. FIG. 2 represents a sectional view of the pearl of the invention, observed with a scanning microscope.
Mesure de la masse volumique des perles Le volume des perles est estimé par déplacement d'eau selon le protocole suivant : Une fiole conique jaugée de volume adapté à la taille des perles est remplie d'eau jusqu'au bord du col, ce qui correspond à un volume V1 d'eau. La masse de l'ensemble fiole+eau est mesurée, on la note M1. L'eau de la fiole est évacuée. La fiole est remplie par une masse m1 déterminée de perles. La fiole est à nouveau remplie d'eau jusqu'au bord du col. Le remplissage est effectué en s'assurant à l'aide d'une grille métallique que le volume rempli est identique à V1 malgré la présence de perles à la surface. La masse de l'ensemble fiole+eau+perle est mesurée, elle est notée M2. La masse volumique de la perle est alors égale à [m1/(M1-M2+m1)]*deau en g/cm3 (deau=1g/cm3)Measurement of the density of the pearls The volume of the pearls is estimated by displacement of water according to the following protocol: A volumetric conical flask of volume adapted to the size of the pearls is filled with water up to the edge of the neck, which corresponds to a volume V1 of water. The mass of the whole flask + water is measured, we denote it M1. The water in the flask is discharged. The flask is filled with a determined mass m1 of pearls. The flask is again filled with water up to the edge of the neck. The filling is carried out by making sure using a metal grid that the filled volume is identical to V1 despite the presence of beads on the surface. The mass of the vial + water + pearl assembly is measured, it is denoted M2. The density of the pearl is then equal to [m1 / (M1-M2 + m1)] * d ea u in g / cm 3 (d ea u = 1g / cm 3 )
EXEMPLES Exemple 1EXAMPLES Example 1
Un mélange de granulés de PA66 commercialisé par la société Rhodia Technical Fibers sous la référence 132J00® (90% p/p) et de granulés de polycarbonate commercialisé par la société Bayer sous la référence Makrolon 2207® (10% p/p), est introduit dans une extrudeuse bivis commercialisée par la société Leistriz sous la référence TSA-EMP 26-35®, équipée d'un système de coupe en tête noyé commercialisé par la société Gala sous la référence LPU Mod 5 . Le profil de température sur les éléments de chauffe de la bi-vis sont (en °C) 270-280-280-280-280-280, l'adapteur est maintenu à 272°C et la filière chauffée à 330°C. La vitesse de rotation des vis est fixée à 201 tours. min"1. Le débit d'extrusion est de 15kg/h. La filière est composée d'un seul orifice de diamètre 2.4 mm. L'eau de coupe est maintenue à 85°C. Le porte-couteaux comporte deux couteaux et la fréquence de coupe est 2800 tours/min On obtient par cette méthode des granulés de polyamide expansés rigides de densité 0.6 g/cm3. La figure 1 représente une vue de dessus de la perle de l'invention, observée au microscope à balayage. On peut observer sur cette figure la peau continue de la perle La figure 2 représente une vue en coupe de la perle de l'invention, observée au microscope à balayage. On peut observer sur cette figure la peau continue de la perle et sa porosité interne.A mixture of PA66 granules marketed by the company Rhodia Technical Fibers under the reference 132J00® (90% w / w) and polycarbonate granules marketed by the company Bayer under the reference Makrolon 2207® (10% w / w), is introduced into a twin-screw extruder sold by the company Leistriz under the reference TSA-EMP 26-35®, equipped with a flooded head cutting system sold by the company Gala under the reference LPU Mod 5. The temperature profile on the heating elements of the twin-screw are (in ° C) 270-280-280-280-280-280, the adapter is maintained at 272 ° C and the die heated to 330 ° C. The screw rotation speed is fixed at 201 turns. min "1. The extrusion rate is 15 kg / h. The die consists of a single orifice with a diameter of 2.4 mm. The cutting water is maintained at 85 ° C. The knife holder has two knives and the cutting frequency is 2800 rpm This is a method of obtaining rigid expanded polyamide granules with a density of 0.6 g / cm 3. FIG. 1 represents a top view of the pearl of the invention, observed under a scanning microscope. The continuous skin of the pearl can be seen in this figure Figure 2 shows a sectional view of the pearl of the invention, observed with a scanning microscope, The continuous skin of the pearl and its internal porosity can be observed in this figure.
Exemple 2 Un mélange de granulés de PET commercialisé par la société Wellman sous la référence Permaclear VI 84® (85% p/p) et de granulés de polycarbonate commercialisés par la société GE Plastics sous la référence Lexan 121 - 111® (15%p/p) est introduit dans une extrudeuse bivis commercialisée par la société Leistriz sous la référence TSA- EMP 26-35®, équipée d'un système de coupe en tête noyé commercialisé par la société Gala sous la référence LPU Mod 5. Le profil de température sur les éléments de chauffe de la bi vis sont (en °C) 280-300-315-335-275, l'adapteur est maintenu à 272°C et la filière chauffée à 330°C. La vitesse de rotation des vis est fixée à 200 tours. min"1. Le débit d'extrusion est de 15kg/h. La filière est composée d'un seul orifice de diamètre 2.4 mm. L'eau de coupe est maintenue à 85°C. Le porte-couteaux comporte deux couteaux et la fréquence de coupe est 2800 tours/min On obtient par cette méthode des granulés de PET expansés rigides de densité 0.7 g/cm3. Example 2 A mixture of PET granules sold by the company Wellman under the reference Permaclear VI 84® (85% w / w) and polycarbonate granules sold by the company GE Plastics under the reference Lexan 121-111® (15% w / p) is introduced into a twin-screw extruder sold by the company Leistriz under the reference TSA-EMP 26-35®, equipped with a submerged head cutting system sold by the company Gala under the reference LPU Mod 5. The profile of temperature on the heating elements of the twin screw are (in ° C) 280-300-315-335-275, the adapter is maintained at 272 ° C and the die heated to 330 ° C. The screw rotation speed is fixed at 200 turns. min "1. The extrusion rate is 15 kg / h. The die consists of a single orifice with a diameter of 2.4 mm. The cutting water is maintained at 85 ° C. The knife holder has two knives and the cutting frequency is 2800 rpm. This method produces rigid expanded PET granules with a density of 0.7 g / cm 3 .

Claims

REVENDICATIONS
1. Procédé de préparation d'une perle à base de polymère expansé et à peau continue comprenant les étapes successives suivantes : a) extruder à travers une filière une composition expansible comprenant un polymère thermoplastique et un agent d'expansion, à l'état fondu, pour réaliser l'expansion b) refroidir et couper le matériau expansé obtenu en sortie de filière à l'aide d'un couteau1. Process for the preparation of a pearl based on expanded polymer and with continuous skin comprising the following successive steps: a) extruding through a die a foamable composition comprising a thermoplastic polymer and a blowing agent, in the molten state , to carry out the expansion b) cool and cut the expanded material obtained at the die outlet using a knife
2. Procédé selon la revendication 1 , caractérisé en ce que l'agent d'expansion est un gaz pouvant se disperser ou se dissoudre dans le polymère à l'état fondu2. Method according to claim 1, characterized in that the blowing agent is a gas which can disperse or dissolve in the polymer in the molten state
3. Procédé selon la revendication 1 , caractérisé en ce que l'agent d'expansion est un agent porogène3. Method according to claim 1, characterized in that the blowing agent is a blowing agent
4. Procédé selon la revendication 1 , caractérisé en ce que l'agent d'expansion est un composé volatile pouvant se dissoudre dans le polymère à l'état fondu4. Method according to claim 1, characterized in that the blowing agent is a volatile compound which can dissolve in the polymer in the molten state
5. Procédé selon la revendication 1 , caractérisé en ce que l'agent d'expansion est un composé chimique pouvant réagir chimiquement avec le polymère par chauffage en générant un gaz.5. Method according to claim 1, characterized in that the blowing agent is a chemical compound which can react chemically with the polymer by heating by generating a gas.
6. Procédé selon l'une des revendications précédentes, caractérisé en ce que le polymère est un polyamide6. Method according to one of the preceding claims, characterized in that the polymer is a polyamide
7. Procédé selon l'une des revendications précédentes, caractérisé en ce que la composition expansible comprend un nucléant et/ou un surfactant et/ou un plastifiant7. Method according to one of the preceding claims, characterized in that the expandable composition comprises a nucleating agent and / or a surfactant and / or a plasticizer
8. Procédé selon l'une des revendications précédentes, caractérisé en ce que la composition expansible comprend des charges de renfort telles que des fibres de verre, des matifiants, des pigments, des colorants, des stabilisants chaleur ou lumière, des agents bioactifs, des agents antisalissure, et/ou des agents antistatiques. 8. Method according to one of the preceding claims, characterized in that the expandable composition comprises reinforcing fillers such as glass fibers, matifiers, pigments, dyes, heat or light stabilizers, bioactive agents, antifouling agents, and / or antistatic agents.
9. Procédé selon l'une des revendications précédentes, caractérisé en ce que le refroidissement lors de l'étape b) est réalisé à l'aide d'un liquide, de préférence à l'aide d'eau.9. Method according to one of the preceding claims, characterized in that the cooling during step b) is carried out using a liquid, preferably using water.
10. Procédé selon l'une des revendications précédentes, caractérisé en ce que la perle obtenue présente un diamètre inférieur ou égal à 10 mm, de préférence inférieur ou égal à 5 mm.10. Method according to one of the preceding claims, characterized in that the pearl obtained has a diameter less than or equal to 10 mm, preferably less than or equal to 5 mm.
11. Procédé selon l'une des revendications précédentes, caractérisé en ce que la perle obtenue présente une masse volumique inférieure ou égale à 0,8 g/cm3, de préférence inférieure ou égale 0,5 g/cm3, encore plus preferentiellement inférieure ou égale à 0,3 g/cm3 11. Method according to one of the preceding claims, characterized in that the pearl obtained has a density less than or equal to 0.8 g / cm 3 , preferably less than or equal 0.5 g / cm 3 , even more preferably less than or equal to 0.3 g / cm 3
12. Perle à base de polyamide ou de polyester expansé présentant une peau continue.12. Pearl based on polyamide or expanded polyester with continuous skin.
13. Perle selon la revendication 12, caractérisée en ce qu'elle présente un diamètre inférieur ou égal à 10 mm, de préférence inférieur ou égal à 5 mm.13. Pearl according to claim 12, characterized in that it has a diameter less than or equal to 10 mm, preferably less than or equal to 5 mm.
14. Perle selon la revendication 12 ou 13, caractérisée en ce qu'elle présente une masse volumique inférieure ou égale à 0,8 g/cm3, de préférence inférieure ou égale 0,5 g/cm3, encore plus preferentiellement inférieure ou égale à 0,3 g/cm3 14. Pearl according to claim 12 or 13, characterized in that it has a density less than or equal to 0.8 g / cm 3 , preferably less than or equal to 0.5 g / cm 3 , even more preferably less than or equal to 0.3 g / cm 3
EP04767525.1A 2003-07-04 2004-06-30 Method for preparing beads based on expanded polymer Expired - Lifetime EP1641608B1 (en)

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FR0308210A FR2856950B1 (en) 2003-07-04 2003-07-04 PROCESS FOR PREPARING PEARL BASED OF EXPANDED POLYMER
PCT/FR2004/001681 WO2005011952A2 (en) 2003-07-04 2004-06-30 Method for preparing beads based on expanded polymer

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BRPI0411643B1 (en) 2017-12-05
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US8529812B2 (en) 2013-09-10
CA2531379A1 (en) 2005-02-10
KR100853979B1 (en) 2008-08-25
FR2856950A1 (en) 2005-01-07
CN100500408C (en) 2009-06-17
EP1641608B1 (en) 2017-12-13
BRPI0411643A (en) 2006-08-08
KR20060039427A (en) 2006-05-08
US20070036967A1 (en) 2007-02-15
FR2856950B1 (en) 2007-03-02
JP2007516307A (en) 2007-06-21
RU2323824C2 (en) 2008-05-10
CN1816435A (en) 2006-08-09
JP4571131B2 (en) 2010-10-27
WO2005011952A2 (en) 2005-02-10
RU2006103266A (en) 2007-08-20

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